1. Field of the Invention
The present invention relates to a motor support structure of an actuator using a motor.
2. Description of the Related Art
A conventional structure for supporting a motor output shaft in an actuator is described in, for example, Japanese Patent No. 3050791, which is configured such that a primary gear is put on an output shaft of a motor, and secondary and other gears are engaged in series with the primary gear so that a driving force of the motor is transmitted via the primary gear to the secondary and other gears in sequence and thereby the secondary and other gears are caused to rotate, wherein bearings for the output shaft of the motor are supported by using elastic members, such as O-shaped rings, which are arranged near a body of the motor, in order to reduce vibration and noise.
In the structure described above, at a side of the output shaft having the primary gear, the O-shaped ring (elastic member) is located axially between the primary gear and the body of the motor.
Also, Japanese Patent No. 4098454 discloses a motor actuator in which a motor is supported in such a manner that the axially front and rear ends of a motor body are pressed by respective pressing ribs formed at front and motor support portions of a case, whereby the motor is fixed at a small area so as to make it difficult for the vibration and noise generated by the motor to be transmitted to the case.
A motor can be fixed to a case by means of an O-shaped ring generally available, but since the ring has a circular configuration, some countermeasures must be taken to prevent a motor body shifting in the direction of motor output shaft rotation relative to the case. As one method of the countermeasures, a part of an outer frame of the motor may be set in touch with the case for preventing rotation of the motor body relative to the case, but this method allows the vibration of the motor to be easily transmitted to the case. This problem may be solved by using a vibration-proofing material but the number of component members is increased.
Also, a structure for supporting the end of an output shaft of a motor may be integrated with a case. However, while the property required for a case material is different from the property required for a bearing material, priority is put on the strength of the case therefore resulting in failure to contribute to the reduction of vibration and noise.